The invention relates to an air spring and damper unit for vehicles, which has at least two working spaces filled with compressed air, in which at least one working space is in each case delimited at least partially by movable walls, in particular by movable walls in the form of roll-type or fold-type bellows, and in which the working spaces are connected to one another via flow ducts, and the flow ducts have throttle valves.
Such air spring and damper units, referred to in brief as air dampers, are known as convenient spring/damper units for the most diverse possible vehicle types, such a damper unit usually being arranged between the body and the chassis.
Thus, DE 101 15 980 discloses a gas spring/damper unit with a piston which is displaceable in a cylinder housing and is sealed off with respect to the latter and which subdivides two working spaces. The damper space is partially delimited outwardly by a roll-type bellows. The throttle valves located in the piston are in this case configured such that, as a function of the throughflow direction, a different flow resistance is present and the location of transfer from a laminar to a turbulent flow is adapted. The throttle valves shown here are permanently set/integrally formed throttles without a regulating function.
DE 199 32 717 A1 discloses a device in which two working spaces of a gas spring/damper unit are subdivided by means of a sealed-off piston displaceable in a cylinder housing. The damper space is partially delimited outwardly by a roll-type bellows. The throttle valves located in the piston are in this case configured as valves loaded by spring washers, the spring washers and valve cross sections being designed as a function of the throughflow direction.
A pneumatic spring/damper unit with electromagnetically controllable overflow valves, the closing members of which are formed by small diaphragms, is known from DE 43 34 007 A1. The magnetic flux runs through the small diaphragms, and the small diaphragms cooperate, in their closing position, with assigned bearing surfaces. The closing force can be varied by means of a controllable electromagnet, so that a spring/damper unit with variable tuning is obtained. With this spring/damper unit, it is possible to set the maximum closing force or prestress and to determine the pressure beyond which the valve opens.
A gas spring/damper unit with overflow throttles which are closed by means of resilient sealing disks is known from DE 101 35 261 C1. The resilient sealing disks are not permanently tension-mounted, but are secured only for a predetermined pressure difference range by means of a spring force. After a specific pressure has been overshot, the tension-mounting region lifts off, the resilient force for loading the sealing disk being applied preferably by means of a likewise resilient annular disk.
The previous embodiments have the disadvantage, however, that a possibility of adjusting the damper characteristic as a function of the respective driving situation with the effect of a changeover of the air dampers to another damping characteristic curve either is present to only a slight extent or is not afforded at all. The dynamic differential pressure at the throttle valves and the volume flow are critical for energy conversion by dissipation and consequently for the damping work. In air damping, high pressures and large volume flows are necessary for generating the required damping work. Influencing the damper characteristic, that is to say the damping characteristic curve, is therefore difficult particularly because, in the gas damping systems present here, high pressures and high volume flows have to be switched.
For the invention, therefore, the object was to provide an air spring and damper unit for vehicles, in which a good adjustability of the damper characteristic is achieved, in which high pressure differences can be switched, in addition to large volume flows, between the working chambers, and which allows adaptation and reaction to different ground and driving situations.
The object is achieved by means of the features of the main claim. Advantageous developments are disclosed in the subclaims.